In the fast food industry, developing an ideal package for sandwiches, french fries, and the like, poses special problems. It is desirable to protect the product, but the package must be inexpensive. The package should occupy as little room as possible when shipped and stored awaiting use. It should be easy to use without much training or skill, and not awkward to close about the product. The package should retain heat, but allow some venting of moisture to prevent sogginess of buns or french fries. Most fast food products that are served warm generate water vapor. If this water vapor is confined by a package in the immediate vicinity of bread products or french fries, it will be absorbed and provide a limp sandwich or french fries which will be much less appetizing to the consumer opening the package.
Conventional package designs for the fast food industry usually provide only one or two of the desirable features listed above. Simple wax paper wrapping sheets for sandwiches, for instance, provide an assembly surface and retain heat to some extent, but also retain moisture. They provide almost no protection against crushing the product.
Open top french fry containers or bags provide considerable ventilation of moisture, but do not retain heat to keep the food warm between cooking and consumption. The air circulation that carries away the moisture also quickly transfers heat away from the food.
Some attempts have been made to combine flexible wrapping materials, which have cost and space-saving characteristics, with paperboard sleeves to help protect sandwiches. These attempts have been less than successful. U.S. Pat. No. 3,964,669 discloses a central rigid member which is folded to surround the sandwich with a rigid sleeve and provide a paperboard handle. An outer flexible sheet attached to the rigid member extends beyond the open ends of the sleeve and must be tucked in or twisted to close the package in an unstable, unreliable fashion. Furthermore, awkward panels formed in the paperboard must be lifted and held back in order to place the sandwich in its proper position. U.S. Pat. No. 4,575,000 discloses an inner layer of glassine type paper and an outer layer of paperboard, again forming a rigid sleeve around the sandwich being wrapped. The extending glassine paper ends of the sleeve must be tucked under the sandwich, so that no positively fastened closure is provided. In using the packages disclosed in these patents, the tucking required to complete the package may result in crushing the contents. Neither the package configuration nor the nature of the flexible material allows moisture to be vented. Furthermore, the principle is followed that the paperboard portion must surround the sandwich and form the top closure over the sandwich.
Other prior patents showing paperboard containers having coated or lined interiors are U.S. Pat. Nos. 1,704,175; 2,011,179; 2,556,321; and 3,627,541.
Thus, a need has existed in the art for a package for warm food items that protects the item, encloses the item and prevents air circulation in order to retain heat, but permits the escape of moisture to prevent the item from becoming soggy.